Effects of Incorporation of Various Amounts of Zirconium Oxide Particles on Microstructure and Mechanical Strength of Conventional and Light-cure Glass Ionomer Cements

Background: The purpose of this study is to investigate the mean compressive strength and microstructure of the light-cure and self-cure glass ionomer by adding 5%, 10%, and 15% zirconium oxide particles. Methods: In this experimental study, 112 specimens in 8 groups including control groups (light-cure and self-cure glass ionomer) and 3 groups containing zirconium oxide particles (weight percentages 5%, 10% and 15%) in light-cure glass ionomer and 3 groups containing zirconium oxide particles (weight percentages 5%, 10% and 15%) placed in self-cure glass ionomer. The specimens were made in a transparent plastic mold with a diameter of 4 and a height of 6 millimeters. Lightcure glass ionomer cements were emitted from the light cure unit after 80 seconds light radiation. Then all specimens were stored in distilled water (37°C) for one day. Then they were subjected to compressive strength test using the Universal Testing Machine (STM- 20) (SANTAM) with 2 N initial force and 0.5 mm/min blade speed). The compressive strength (MPa) was analyzed by one- way ANOVA and HSD post hoc tukey (p<0.05). Results: In light-cure glass ionomer groups, the highest and lowest mean compressive strength were observed for groupe containing 15% w zirconium oxide particles (228.51) and control group (170.44). In the self-cure glass ionomer group, the highest and lowest mean compressive strength were observed for groupe containing 10% w zirconium oxide particles (36.04) and control group (30.58). Conclusion: Based on the results of this study, it can be concluded that the addition of zirconium oxide particles 15% w in light-cure glass ionomer increases the mean compressive strength.